CONTRIBUTION OF THE PERIPHERAL CHEMORECEPTORS TO THE VENTILATORY RESPONSE TO CO2 IN ANESTHETIZED CATS DURING HYPEROXIA

Experiments were performed on nine adult cats anaesthetized with chloralose and urethane. The ventilatory response to CO2 during hyperoxia (FlO2) was determined before and after denervation of the peripheral chemoreceptors. We observed flattening of the upper part of the CO2 response curve occurring at lower levels of V̇e after vagotomy. The part of the V̇e vs. PaCO curve could be described by a linear relation with slope S and intercept B at zero ventilation. In four cats both the slope and B value remained essentially the same after vagotomy. After subsequent sinus neurotomy a reduction in S in the range of 32-46% (mean 41%) was observed with no systematic change in B. In five cats the sequence of the denervation procedures was reversed. After carotid chemodenervation the slope decreased in the range of 23-54% (mean 41%) with no systematic change in B. When subsequent vagotomy was performed the changes in slope were negligible, except for one experiment where a further reduction in slope of 15% was observed. The arterial blood pressure and the stability of the respiratory variables tended to be more affected when both vagotomy and sinus neurotomy were performed. It is concluded from the slope reductions that in the presence of hyperoxia the contribution of the carotid chemoreceptors to the respiratory response to CO2 amounts to about 40%, and that the relative contribution of the aortic bodies to the ventilation is negligible. © 1978.